Glaucoma affects more than 65 million people worldwide and is expected to affect about 80 million people in 2020. It is second only to cataracts in frequency of causing blindness in the global world. Glaucoma is characterized by a progressive loss of retinal ganglion cells, a characteristic optic neuropathy and patterns of visual field loss in the more advanced stages. The pathogenesis of glaucoma is multifactorial with several recognized risk factors of which increased intraocular pressure (IOP) is the most important one.
Normal IOP ranges between 10 to 21 mmHg with an average of 15.3 mmHg. Lowering IOP by medications or surgery is the only therapeutic modality currently available. Therefore, IOP measurements are of great importance for glaucoma diagnosis, management and follow-up during medical or after surgical treatment.
The most widely used method of measuring IOP is Goldmann applanation tonometry (GAT), which is performed by measuring the force required to flatten a predefined area of the cornea with a hard surface device. Unfortunately, the accuracy of IOP measurements by GAT is affected by several factors such as corneal thickness as well as other corneal biomechanical properties. Aside from measurement errors, another major drawback of the GAT method is the complexity of the technique. There is also a need for topical anesthesia since the applanator is in direct contact with patient's cornea. Obviously, this procedure cannot be performed by the patients themselves, their relatives or by any other non-professional personnel, and cannot be done routinely in the supine position.
Accordingly, it is clear that since IOP is highly fluctuating, occasional measurements of IOP in the clinicians' office are not sufficient for glaucoma management and there is a need to develop technology that will enable more frequent or home monitoring of IOP in selected cases of glaucoma patients. The present invention addresses this need.